While handheld devices such as cell phones, Personal Digital Assistant (PDA) etc. become indispensable in daily life, the capability to support multi-language entry is lagged behind. English and Chinese are the two most commonly used languages in the world. Yet convenient entries for English and Chinese letters are essential yet unmet needs in hand held devices.
The handheld devices have to be carried around so the devices must be as compact as possible. Therefore their keypads must be small and light weighed to fit the device. On the other hand, their key buttons must be as big as possible for easy fingertip manipulation. As the size of the handheld devices and keypad real-estate continues to shrink, it is difficult to support a large number of keys. On the other hand, the demands for numerical plus multi-language entry are increasing due to globalization and closer social-economical ties between different countries and regions with different languages.
There is a pressing need for keypad optimization to achieve not only versatile language support but also small and compact for handy carry and storage. An optimally designed handheld device must be                (1) allows Multilanguage letters to key-button mapping for efficient multi-language entry,        (2) small enough for hand carry and,        (3) big enough key-button for finger tips to conveniently and precisely type the keys and optimally shaped to fit the stylish design.        
Prior art approaches map multiple letters to one key and require users to type multiple strikes to enter the desired letter. There are two primary types of keypads for handheld devices: (1) number-pad and (2) qwaz-pad.
A. Number-Pad:
A popular number-pad is the phone pad which is widely used on telephone sets. To hold the 10 digits (0, 1, 2 . . . 9) for phone number dialing, the traditional phone pad is a 10-button keypad. A variation of number-pad is the number pad, which can be seen in calculator or on the right side of computer keyboards for number entry.
To support the English language entry based on the number-pad, the 26 English letters are grouped and 3-to-1 mapped to the key buttons. This type of keypad is commonly used in cell phone applications. The drawback of the 10-key keypads for English entry is that one may need up to three strikes to enter a single English letter.
The Chinese language has 42 phonetic letters, more than the number of letters in English. To support Chinese language entry, traditionally, the 42 phonetic letters are grouped and then mapped to the 10-key buttons in cell phone applications. An example of such Chinese phonetic to key button mapping is a “4-to-1” mapping. In this case, one may need up to around 4 strikes to enter each phonetic letter, which is even worse than that in English language entry,
B. Qwaz-Pad and Squeezed Qwaz-Pad:
The traditional qwaz-pads are derived from the traditional PC/terminal keyboards. The qwaz-pad has 3 rows of 10-column buttons to hold the 26 English letters for data entry.
While most cell phones use 10-key handy keypads, some high-end smart phones use qwaz-pad for English language entry. For handheld device language entry, the qwaz-pad has a fatal drawback due to its 10-column width: (1) The qwaz-pads' 10-column width is too wide, and therefore is difficult for a single-hand manipulation to simultaneously hold and hit keys with finger tip, especially comparing with the 3-column number-pads. (2)
The 10-column width is too wide, makes handheld device “fat” in shape, and is therefore very difficult to meet the stylish design needs in the marketplace.
To overcome the 10 column drawback, the qwaz-pad keypad can be squeezed into a squeezed keypad with only 14 keys and a 2-to-1 letters-to-button mapping. The squeezed qwaz-pad can better meet the stylish design requirement. However, one might need up to 2 strikes to enter a single English letter with the squeezed qwaz-pad for English letter entry.
As cell phones and electronic handheld devices become more and more popular in the modern life, each device needs to have not only a handy keypad, but also the capability of supporting universal (e.g., Chinese, Japanese, etc.) character data input. The existing 10-key number-pad, 26-key qwaz-pad and squeezed qwaz-pad designs have the following problems:                1. The 10-key number-pad has far fewer than the number of 26 English letters and 42 Chinese phonetic letters, which requires many to one mapping and makes number-pad difficult for language entry.        2. The 26-key qwaz-pad has 10 columns on each row.                    i. If regular size button is used, the keypad exceeds reasonable device width, and hence very “fat”, not convenient to carry, and difficult for a single hand to simultaneously hold and type.            ii. When forced to shrink the 10-column key buttons to fit in a single hand handy handheld device, the buttons are too small for finger tips to type.            iii. When the 10-column buttons are squeezed into 14-key buttons, each button is assigned two letters, which makes double strikes needed and brings down language letter entry efficiency.                        3. Chinese language needs 42 phonetic symbols for data input. Both the traditional number-pads and qwaz-pads with existing letter allocations are very difficult for Chinese language entry.        
Other prior art methods are described in M. D. Dunlop. “Watch-Top Text-Entry: Can Phone-Style Predictive Text-Entry Work With Only 5 Buttons?.” Proceedings of MobileHCI 04. September 2004., Hedy Kober 1 , Eugene Skepner 1, Terry Jones 1, Howard Gutowitz 1,2, and Scott MacKenzie “Linguistically Optimized Text Entry on a Mobile Phone”, Conference on Human Factors in Computing Systems, 2001, MacKenzie, I. S., Kober, H., Smith, D., Jones, T., Skepner, E. (2001). LetterWise: Prefix-based disambiguation for mobile text input. Proceedings of the ACM Symposium on User Interface Software and Technology—UIST 2001, pp. 111-120. New York: ACM, Connolly, et al. U.S. Pat. No. 6,005,495, Method and system for intelligent text entry on a numeric keypad, Dec. 21, 1999; King, et al., U.S. Pat. No. 6,011,554, Reduced keyboard disambiguating system, Jan. 4, 2000; Gutowitz, H. U.S. Pat. No. 6,219,731, Method and apparatus for improved multi-tap text input. Eatoni Ergonomics, Inc. Apr. 17, 200; and a survey is conducted in “A Survey of Alternate Text-Entry Methods”, 2000 Eatoni Ergonomics, Inc., www.eatoni.com (2000). Unfortunately, none of the prior methods are suitable for multi-language entry, especially involving Chinese and English.